PIE model

An example of an abstract formal model—that is, one that is used to analyze a class of systems and usability problems rather than specifying a particular system. The PIE model was developed at York University in the mid-1980s and was one of the first steps in a new stream of formal method work in human-computer interaction (HCI) that began at that time. See: http://www.hcibook.com/alan/topics/formal/

practice

When being trained as a carpenter or a nurse, for example, one shares a practice. At the same time, each individual who possesses a practice keeps it up and changes it as well. It is practice that allows us to talk about more than just individual skills, knowledge, and judgment, and not just about a “generic” human being. Practice is shaped historically, which is of particular relevance for design and use of computer applications.

preattentive processing

The rapid detection of visual features theorized to occur in parallel before the operation of selective attention.

predictive model

A model that allows metrics of human performance to be determined analytically without undertaking time-consuming and resource-intensive experiments.

Problem Behavior Graph

A graphical depiction of search through a problem space.

problem solving

Searching through a problem space from a known start state to a desired end state, or one of a set of desired end states, applying operators of uncertain outcome to move from state to state. Problem solving typically refers to a path through the problem space that includes explorations of deadend paths and backing up to prior states. (see skilled behavior for a contrasting type of behavior)

problem space

A mental representation of a problem, including the start state, the goal state, and the operators or moves that allow transitions between states. According to Newell and Simon’s (1972) theory of problem solving, humans solve problems by constructing and searching a problem space.

procedural knowledge

Also called “how to do it” knowledge. The knowledge of which operators to perform to move from a known start state to a desired state in a problem space.

Production system

A programming language made up of conditional statements. If all conditions are satisfied, then action is taken.